A top U.N. envoy will tell President Bashar Assad on Saturday that Syria will face political and economic isolation if he does not completely and quickly withdraw from Lebanon, U.N. and U.S. officials were quoted as saying on Friday.

In the Saturday's meeting in Damascus, Terje Roed-Larsen plans to inform Syria that the international community is united in insisting that the latter comply with U.N. Resolution 1559 -- and is ready to impose wide punitive sanctions if it does not act quickly, the officials said, according to The Wshington Post.

"If he doesn't deliver, there will be total political and economic isolation of his country. There is a steel-hard consensus in the international community," a senior U.N. official said.

In preparation for the diplomatic confrontation, Roed-Larsen has met over the past week with top U.S., European and Arab officials to determine the positions and parameters of action. In a final round of talks, he met Thursday with Egyptian President Hosni Mubarak and also won backing from the Arab League in talks with its secretary general, Amr Mousa, earlier this week -- discussions aimed at leaving Syria no political escape routes, the source said.

Roed-Larsen will tell Assad that he must take four steps, U.S. and U.N. officials conveyed. First, Syria must honor the independent sovereignty of Lebanon and not undermine its spring elections for a new parliament.

Second, Assad must provide a complete timeline for a full pullout of troops. Third, Damascus must provide a timeline for the pullout of 5,000 intelligence agents in Lebanon. Finally, Roed-Larsen will discuss other requirements in Resolution 1559, including the need to disarm and dismantle foreign and domestic militias operating in Lebanon, all of which Syria supports, U.N. and U.S. officials said.